I suspect the workbook has corruption within it. Let's see if we can fix it.
Open the workbook.
Use File > Save As and choose a new file format, such as .xls (the old format for Excel) and then save the workbook.
Quit Excel (Command-Q)
Now open the saved .xls file and reverse the procedure using File > Save As and choosing .xlsm file format.
Quit Excel (Command-Q)
Now try opening the workbook
Is the workbook fixed?